1. Field of the Invention
The present invention relates to the fields of molecular biology and oncology and provides novel methods for the detection of carcinoma metastases by nucleic acid amplification. In a preferred embodiment, carcinoma metastases are identified in hematopoietic tissues by detection of normal non-hematopoietic RNA expressed by the metastatic carcinoma cells. Detection of non-hematopoietic RNA sequences indicates the presence of metastatic disease. The methods have applications in the diagnosis, staging, and monitoring of carcinoma patients.
2. Description of Related Art
Recent advances in cancer therapeutics have demonstrated the need for more sensitive staging and monitoring procedures to ensure initiation of appropriate treatment, to define the end points of therapy and to develop and evaluate novel treatment modalities and strategies. In the management of carcinoma patients, the choice of appropriate initial treatment depends on accurate assessment of the stage of the disease. Patients with limited or regional disease generally have a better prognosis and are treated differently than patients who have distant metastases (Minna et al., 1989, Cancer Principals and Practices of Oncology, DeVita et al. ed. Lippincott, Philadelphia pp. 591-705, which is incorporated herein by reference). However, conventional techniques to detect these metastases are not very sensitive.
For example, the prognosis and therapeutic management of both major histological subgroups of lung cancer (small cell and non-small cell) depend upon the stage of disease activity at the time of diagnosis (Green, 1989, Lung Cancer 5:178-185, which is incorporated herein by reference). Patients with non-small lung cancers cell (NSCLC) comprise approximately 75% of lung cancers. This histological subgroup of lung cancer has been considered relatively resistant to chemotherapy. However, NSCLC are often curable by surgical resection (and occasionally by radiation therapy) in patients with stages I,II, or IIIA disease who do not have occult distant metastases.
Unfortunately, conventional staging procedures to detect metastatic disease are not very sensitive. Approximately 25% to 30% of stage I NSCLC patients are not cured by primary tumor resection because they have metastases that are not identified by standard methods during preoperative staging. The development of more sensitive techniques to detect metastases could identify those NSCLC patients who will not be cured by local surgical rumor resection, who would benefit from the administration of effective systemic therapies. Similarly, more sensitive methods to detect metastases in other types of carcinomas would identify patients who will not be cured by local therapeutic measures, for whom effective systemic therapies would be more appropriate.
The inadequacy of current staging methods also adversely effects the management of the other major histological type of lung cancer, small cell lung carcinoma (SCLC). In contrast to NSCLC, SCLC is very sensitive to chemotherapy and radiation therapy but is generally believed to be incurable by surgery alone since these minors have usually metastasized to distant sites at the time of diagnosis. Approximately 25% to 35% of limited disease patients who achieve complete remissions with therapy have durable remissions, and two years event-free survival, following treatment. Current staging procedures cannot distinguish those who will have earlier relapses despite achieving initial complete remission. Most SCLC patients who achieve complete remissions have minimal residual disease (MRD) which cannot be detected by conventional methods. More sensitive methods to detect metastases are needed for identifying limited disease patients at high risk for early rumor recurrence who may benefit from additional systemic therapy.
Immunocytological procedures have been used to detect cancer cells in peripheral blood and bone marrow specimens unsuspected on the basis of conventional morphological evaluations (Sobol et al., 1982, Clin. Immunopathol. 24:139-144, and Sobol et al., 1985, Cancer 56:2005-2010, incorporated herein by reference). Immunohistochemical and immunofluorescence techniques have been used to identify antigens expressed by carcinomas that are not expressed by hematopoietic tissues (Sobol et al., 1986, Cancer Research 46:4746-4750, and Sobol et al., 1987, Ann. Intern. Med. 105:698-700). Several investigators have employed monoclonal antibody immunocytology to detect bone marrow metastases in carcinoma patients not identified by standard morphological examinations (Cannon et al., 1988, Eur. J. Cancer Clin. Oncol. 24:147-150; Berendsen et al., 1988, J. Clin. Pathol. 41:273-276; and Stahel et al., 1985, J. Clin. Oncol 3:455-461). However, immunocytological and standard morphological evaluations can reliably detect only 1% to 5% malignant cells in a mixed population with normal hematopoietic cells (Wright et al., 1987, J. Clin. Oncology 5:735-741).
Nucleotide amplification techniques provide rapid and sensitive methods for detecting specific nucleotide sequences (Mullis et al., 1986, Cold Spring Harbor Symposium Quant. Biol. 51:263-273, and Saiki et al., 1988, Science 239:487-491, which are incorporated herein by reference). Cell mixing experiments have demonstrated that polymerase chain reaction (PCR) analysis can identify as few as 1:10.sup.4 or 1:10.sup.5 cells that contain a target gene sequence (Kawasaki et al., 1987, Proc. Natl. Acad. Sci. USA 85:5698-5702, and Crescenzi et al., 1988, Proc. Natl. Acad. Sci. USA 85:4869-4873, which are incorporated herein by reference).
PCR has been employed to detect minimal residual disease activity in patients with hematopoietic malignancies (Fey et al., 1991, Eur. J. Cancer 27:89-94, and PCT Patent Publication No. WO 89/087 17). These methods rely on the identification of abnormal nucleotide sequences resulting from recurring chromosome translocations which characterize the hematological malignancy. Primers flanking the chromosome break points are employed to amplify the aberrant nucleotide sequences which result from the translocation event. In contrast, recurring chromosome translocations are not a common feature of carcinomas. Some carcinomas are characterized by aberrant oncogene or tumor suppressor gene nucleotide sequences (Cooper, 1990, Oncogenes Jones and Burnlett Publishers). However, these abnormal nucleotide sequences are either too diverse, poorly characterized, or infrequent to serve as targets for a practical, generally applied nucleic acid amplification procedure to detect metastatic carcinomas. Novel methods are needed to exploit the sensitivity of nucleic acid amplification procedures to detect metastatic carcinoma disease activity. The present invention meets these needs.